Various procedures and apparatuses are known for the measuring of the length of fibers. These procedures divide themselves mainly into two categories, the one being dedicated to single fiber measurement, and the other dealing with fibers in bundles. In the case of the single fiber measurement those fibers, especially the fibers present in fiber bands, for instance the fiber band of a carding machine, are again dispersed. This is accomplished by a stretchworks or a disintegrator, with the alternate possibility of carrying out the operation pneumatically or even by hand. The individual fibers are subsequently measured either with the equivalent of a ruler or, for instance, by electronic methods. As to the latter, the fibers pass a light relay with the help whereof signals may be gathered which serve for the measurement of the fiber length.
Where bundled fibers are concerned, the entire bundle is placed under mechanical tension, whereby the fibers orient themselves more or less in parallel. The fibers are then subjected to a line sensor. The line sensor can be mechanical, optical, or capacitive, which will work-up a so-called packing-diagram which can be applied to the determination of the length of the fibers being stacked.
These procedures possess in common the disadvantage that during the measurement the fibers are not fully stretched out, or are not lying parallel to one another, or in an unfortuitous situation are subject to both. This disadvantage leads to inexactness in the measurement because in measuring systems for fiber length up to this time, these positional aberrations were not compensated for.
Besides this, the known measuring devices have the disadvantage in that for the most part, they can be automatized only with great difficulty.
A principle purpose of the present invention is to propose a method and a device for measuring the length of fibers, wherein the disadvantages of the state of the technology are overcome and a simple, at least partial, automatization is enabled and an exact measurement of the length of the individual fiber is made possible.
Additional objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
By means of capturing the fiber optically in two projection planes, the goal is advantageously reached that regardless of in which position the fiber is found, or whether the fiber is found in a stretched condition or not, its length is optically fixed and can be measured. When two projection planes are employed, however, the true length of the fiber is exhibited. Particularly advantageous is the situation wherein the two projection planes stand essentially at right angles to one another. The achievement thereby is that a perfect, projected depiction of the fiber becomes possible so that the exact length of the fiber can finally be determined regardless of how much the fiber in its orientation departs from the ideal straight line. A particularly simple method can be set up utilizing these advantages in which one camera for the photographing of at least one projection is a xe2x80x9cline-cameraxe2x80x9d which delivers line shaped images. A plurality of images taken in a short time-period sequence, that is to say, reproductions on the projected plane, produce images, which when considered with knowledge of the velocity of the fibers, yield the projection of the fiber in the plane parallel to the line-camera.
If the fiber, in its composite entirety, is optically imaged over a short period of time in both projection planes, and the exact, instantaneous projected length of the fiber is captured, then the goal can be achieved that the influences which are to be ascribed to the speed of the fiber, can be practically totally eliminated. In this way, the achievement is made that an exact optical reproduction of the fiber is brought about.
For this purpose, advantageously, the fiber can be illuminated during a short time interval which can be done by a flash generator, which can be activated by a stroboscope.
In doing this, it is particularly advantageous to so control the flash that the fibers are detected by a sensor, and this sensor activates the flash. The light flash is then generated when the fibers place themselves in an optimal position in relation to the measurement system. For this purpose, the sensor is connected with the flash by means of a control line. The flash can then illuminate the fibers in the line of sight of the of the optical measurement system, or if preferred in the reverse direction with counter incidence light.
It is advantageous to so spatially install the two projection planes upon which the fibers are to be depicted or captured, that their intersection line runs essentially parallel to the direction of transport of the fibers. By this alignment, the favorable situation is reached in which the fibers in both projection planes are pictured in an advantageous, essentially stretched condition. By means of the conveyance of the fiber by the transport air, the fiber extends itself advantageously in the direction of flow and is at least preponderantly stretched and is so displayed on the projection planes. For the measurement of the length of the fiber, advantageously the projection is dissected into individual image points. The two projection planes together are graduated into a two-dimensional coordinate system. This permits the distance differential of individual points of the picture to be picked out. Now, the image of the projection of the fiber finds itself in the projection planes, and by viewing the two dimensional coordination system, the exact length of the projection of the fiber is depicted in exact length. This can be determined by the distance apart of the individual image points.
In carrying this out, it is particularly advantageous to dissect the projection of the fiber into as many points as possible whereby an especially exact measurement of the length is possible. At best, the dissection of the image points is done for each of the two projections of the fiber.
Providing the same number of image points for each of the two projections is highly recommended. For instance, this can be achieved by two line-cameras so that each optically captures its respective fiber at the same time.
A particularly favorable arrangement is when the image points of the projection coincide exactly with the points of the true fiber, because in this way the purpose will be achieved of an exact length determination of the fiber. By means of a common coordinate axis, the two coordinate systems of the projections will favorably enable attaining the purpose in a simple way. For the determination of the true length of the fiber, the coordinates of the projected image points are assigned numerical values, and the length of the fiber can be determined by processing in a computer. For this reason, the described computation of   L  =            ∑              i        =        1            n        ⁢                                        (                                          x                i                            -                              x                                  i                  +                  1                                                      )                    2                +                              (                                          y                i                            -                              y                                  i                  +                  1                                                      )                    2                +                              (                                          z                i                            -                              z                                  i                  +                  1                                                      )                    2                    
for computer data processing of the numerical values of the coordinates of the projected image points can be advantageously employed.
By the application of a measuring system with at least one camera, an apparatus for the separation of the fibers, and a computer, the goal can be attained that the invented method can be executed in a simple manner.
Particularly advantageous for the separation of the fibers is a rotatable roll circumferentially inset with needles or teeth. These are used because they can separate the fibers especially safely and at the same time protect them. Advantageously, a duct for the transport of the fibers up to the camera point can be installed, because thereby an exact positioning of the now separated fibers in relation to the camera, that is the optical system, is assured. At best, the measurement system will have a sensor which monitors the fibers, and for instance can be placed near the camera for the control of the device. In order to enable a reliable, optical capture of the fibers, the measurement system is provided with a lamp for the illumination of the fibers. Advantageously this lamp comprises a flash or a stroboscope. Favorably, in this case, the sensor is connected over a control line with the flash in order to illuminate the fiber at the correct instant. In a further advantageous embodiment, the device in accord with the present invention includes a mirror which reflects an image of the fiber to be measured in the direction of the camera. The advantage of this arrangement lies therein that it is possible to capture both projections with only one camera.
Particularly advantageous is a sensor to determine the velocity of the fibers, because in this way advantageous line-cameras can be used for the generation of the projection of the fiber. The computer unit can, along with the measurement values, advantageously determine the projection of the fibers and present these in a coordinate system.
By an additional invented procedure, advantageously the thickness of a fiber can be determined. For this purpose, the projection is so additionally processed that first in the image of the fiber, a center line is established across which a perpendicular line is erected. Thus, the intersection of the perpendicular line with the depicted outlines of the fiber is determined. The length differential between these peripheral lines, one to the other, yields a measure for the thickness of the fiber. Along the length of the fiber, a multitude of perpendicular lines intersecting the center line may be drawn, generating also a plurality of outline intersecting point pairs. The number thereof is chosen in accord with the desired degree of exactness for the statement of fiber thickness. With this invented method, advantageously even the variation in the thicknesses of the fiber along its length can be determined.